The USA, under Kennedy had sponsored one invasion of Cuba, which came unstuck at the Bay of Pigs. Inviting in a bunch of nuclear missiles was intended as a way of deterring another invasion.

In responding to the invitation Khruschev was doing what the USA had done any number of times over the previous decade and a half, which was how it had come about that there were nuclear missiles and nuclear bombers sited all around the place pointing at the USSR.

The most remarkable thing about it all was that, having promised not to mount any more invasions of Cuba, as a quid pro quo for having the missiles removed, the USA has actually kept that promise, even after the USSR had collapsed. That's quite impressive, honourable even.

Of course, how long that kind of honour can be relied on under the present regime is perhaps another matter.